Historically, mortar and stucco was made by mixing lime putty with sand and water on a job site. The lime putty typically was made at the job-site from quick lime and water, but prior to use, it had to be aged for several months in an earthen pit. Additives were added to the mortar or stucco to change its behavior and permanence. These additives included pozzolans, blood, animal fiber, vegetable fiber, cactus juices, and clay, to name some of the more common ones. This method was conventional up to the late 19th century.
These mortars and stuccos had only a compressive strength of about fifty to a few hundred pounds per square inch after 28 days, but they continued to gain strength for many months. They also tended to remain flexible and maintained good bond (as related to the compressive strength) and maintained excellent extent of bond. As a result, water penetration through walls at the brick/mortar interface was slight. Further, excess hydrated lime in the system led to autogenous healing in the event a crack occurred at the brick/mortar interface. Disadvantageously, this mortar and stucco took an extended time to cure. As such, only a few rows of brick could be laid per day, and a brown coat could not be added to the scratch coat on a stucco application for a week or more.
With the advent of Portland Cement in the later part of the 19th century, small amounts were added to the mortars and stuccos to reduce the time of set. With time, larger amounts of Portland Cement were added to further reduce the time of set. A positive effect of the added cement was increased early compressive strength. This higher compressive strength was equated with higher quality. However, higher compressive strengths generally correspond to less flexibility of the mortar and, thus, a more brittle characteristic. As such, in areas with high wind, or other loads, this may not be a desirable characteristic. Regardless, these mortars and stuccos tended to maintain good bond and maintain excellent extent of bond. Also, autogenous healing occurred in these cement/lime mortars such that water penetration through walls at the brick/mortar interface was slight.
Improvement to the 19th century technology occurred in the early 1930's when finely divided hydrated lime became available in bags. This resulted in the lime not having to be slurried and aged on the job-site, or if it was, the time of aging was reduced to a matter of days.
As a convenience to the tradesmen using a mortar, masonry cement was developed and was marketed in the 1930's. The masonry cement of the 1930's typically consisted of cement clinker and limestone ground together with vinsol resin as an air-entraining agent and as a grinding aid. This product allowed the tradesman to mix the masonry cement, sand, and water to obtain a mortar. This eliminated the need to produce lime putty on the job site and reduced the potential for errors in mixing hydrated lime and Portland Cement. The proportions of the cement clinker and the limestone would be adjusted to produce an acceptable compressive strength To make the mortars workable, as much as 22% air was entrained into the mortars. The amount of entrained air was regulated by the amount of vinsol resin added to the mix before milling
Unfortunately, the limestone and entrained air did not provide bond. Therefore, the bond strength of mortars and stuccos made with this masonry cement usually was not very good. Also, there was little or no unreacted hydrated lime in the system, and since the Portland Cement in the system was usually fully hydrated, autogenous healing did not occur. The cement, which provided a non-flexible binder, further aggravated the problem. With movements of the wall, the extent of bond could gradually be decreased. Accordingly, numbers of individuals and companies have developed improvements to masonry cement and mortar, as well as to stucco and other hydraulic cements over the years.
Definitions that are used commonly in the industry and as will be used throughout the instant specification and claims are as follows:
Where “ASTM” prefaces a paragraph, the definition in that paragraph was taken directly from an ASTM standard.
Air Content (of Freshly Mixed Mortar)
ASTM The volume of air (or other gas) voids in freshly mixed cement mortar usually expressed as a percentage of total volume of the mortar.
Air Entraining Agent
A chemical that is blended with a cement to increase the amount of entrained air in the mortar or concrete mix. Vinsol resin and various sulfonates are commonly used.
Cement, Hydraulic
ASTM A cement that sets and hardens by chemical interaction with water and is capable of doing so under water.
Portland cement is a hydraulic cement.
Cement, Hydraulic, Blended
A hydraulic cement that is produced by blending two or more components and meets either ASTM C-595 or ASTM C-1157. Type IP cement is made by blending a pozzolan with a Portland cement
Cement, Masonry
ASTM A hydraulic cement for use in mortar for masonry and plastering construction, containing one or more of the following materials: Portland cement, Portland blast furnace slag cement, Portland-pozzolan cement, natural cement, slag cement, or hydraulic lime; and in addition usually containing one or more materials such as hydrated lime, limestone, chalk, calcareous shell, talc, slag, or clay as prepared for this purpose.
Cement Mortar
A mixture of cement, sand, and water, and possibly other ingredients, into a paste like consistency.
Cement, Mortar
ASTM A hydraulic cement, primarily used in masonry construction, consisting of a mixture of Portland blended hydraulic cement and plasticizing materials (such as limestone or hydrated or hydraulic lime), together with other materials introduced to enhance one or more properties such as setting time, workability, water retention, and durability.
Cement, Plastic
ASTM A hydraulic cement, primarily used in Portland cement-based plastering construction, consisting of a mixture of Portland or blended hydraulic cement and plasticizing materials (such as limestone or hydrated or hydraulic lime) together with other materials introduced to enhance one or more properties such as setting time, workability, water retention, and durability.
Cement, Portland
ASTM A hydraulic cement produced by pulverizing Portland-cement clinker, and usually containing calcium sulfite.
A cement that meets the ASTM C-150 standard.
Cement, Portland, Clinker
ASTM A clinker, partially fused by pyroprocessing, consisting predominately of crystalline hydraulic calcium silicates.
Cement Portland Type I
A Portland cement for general use.
Cement, Portland Type II
A Portland cement designed to provide moderate sulfate resistance.
Cement, Portland Type III
A Portland cement designed to provide high early strength.
Cement, Portland Type IV
A Portland cement designed to provide low heat of hydration
Cement Portland Type V
A Portland cement designed to provide high sulfate resistance.
Cement, Stucco
Same as plastic cement Stucco cement tends to be used in the east and plastic cement tends to be used in the west
CMU
Concrete masonry unit. This can range from concrete block to concrete brick.
Concrete
ASTM A composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggregate; in hydraulic-cement concrete, the binder is formed from a mixture of hydraulic cement and water.
Fly Ash
ASTM The finely divided residue that results from the combusting of ground or powdered coal and that is transported by flue gases
Fly Ash, Class C
ASTM Fly ash normally produced from lignite or subbituminous coal that meets the applicable requirements for this class as given herein. This class of fly ash, in addition to having pozzolanic properties, also has some cementitious properties. (ASTM C618)
Class C fly ash usually consists of a mixture of amorphous silica and alumina and crystalline calcium-silicates and calcium-aluminates
Fly Ash, Class F
ASTM Fly ash normally produced from burning antracite or bituminous coal that meets the applicable requirements for the class as given herein. This class fly ash has pozzolanic properties. (ASTM C-618)
Texas lignite also produces a Class F fly ash. Class F fly ash usually consists of a mixture of amorphous silica and alumina.
Fly Ash, Martin Lake
A Class F fly ash produced at the Martin Lake Power Plant near Tatum, Tex. The plant burns Texas lignite.
Fly Ash, Parish
A Class C fly ash produced at the Parish Power Plant near Houston, Tex.
Fly Ash, Rockdale
A Class F fly ash produced at the ALCOA Power Plant near Rockdale, Tex. The plant burns Texas lignite.
Lime
Lime is a general term that includes all forms of burned lime: quick lime, hydrated lime, and hydraulic lime. Limestone and precipitated calcium carbonate are occasionally erroneously referred to as lime.
Lime, Hydrated
ASTM A dry powder obtained by treating quicklime with water enough to satisfy its chemical affinity for water under the conditions of its hydration.
Lime, Hydrated, Dolomitic
Hydrated lime that contains a significant amount of magnesium.
Usually it contains 35% to 40% magnesium compounds (usually MgO and Mg(OH)2) and 60% to 65% calcium compounds (usually CaO and Ca(OH)2). Since it is more difficult to hydrate the magnesium compounds, this lime, when used for masonry purposes, is usually pressure hydrated
Lime, Hydrated, Double
Hydrated lime that has been produced by a pressure hydrator. The lime has not been hydrated twice, but this is the vernacular of the trade.
Life, Hydrated, High CALCIUM
Hydrated lime that contains in excess of 95% calcium compounds.
Lime, Hydrated, Magnesian
Hydrated lime that contains between 5% and 35% magnesium compounds and 65% and 95% calcium compounds.
Lime, Hydrated, Pressure
Hydrated lime that has been produced by a pressure hydrator.
Lime, Hydrated, Type N
ASTM Normal hydrated lime for masonry purposes.
ASTM C-207 does not have a requirement on un-hydrated oxides, or for plasticity.
Lime, Hydrated, Type S
ASTM Special hydrated lime for masonry purposes.
ASTM C-207 limits the un-hydrated oxides to 8% and requires a plasticity figure of not less than 200 within 30 minutes of mixing with water.
Lime, Putty
Lime putty is quick lime that has been slaked and stored in a putty consistency for an extended period of time. The traditional method was to slake and store in a covered ditch (18″ wide by 36″ deep and covered with ^″ soil) for 6 months or more. The process produced maximum workability since all or most hard-to-hydrate particles were fully hydrated. In more recent years water is added to hydrated lime in containers and it is stored for a few days prior to use.
Masonry
A general term for brick, stone, block or other similar materials combined with a mortar.
Mortar
A mix consisting of usually a cementitious binder and a fine aggregate that is used to position and hold brick, block, stone, or other similar materials into permanent position.
Polymers
Modifiers for mortar and stucco that add one or more special properties. Those properties in fresh mortar are usually related to entrained air, amount of water needed, or water retention. In set mortars those properties are usually related to flexural bond, water absorption, or water resistance.
Pozzolan
A substance which in itself is not a cement but when combined with moisture and hydrated lime under ambient temperature conditions will produce cementitious properties. Pozzolans are usually amorphous silica, amorphous compounds will be slightly dissolved and then will combine with the calcium source to form hydrated mono-, di-, and tri-calcium silicates, aluminates, and ferrates. These are the same compounds that form when Portland cement is hydrated.
Pozzolan, Class C
A man-made pozzolan that meets the standards defined in ASTM C-618. The combination of the concentrations of silica, alumina, and iron are between 50% and 70%. Usually this class of pozzolan has some natural cementing properties from the calcium silicates, aluminates, and ferrates that it contains. Examples of Class C pozzolans include fly ashes made with sub-bituminous coal, such as Wyoming coal, and some lignites.
Pozzolan, Class F
A man-made pozzolan that meets the standards defined in ASTM C-618. The combination of the concentrations of silica, alumina, and iron are between 70% and 100%. Usually this class of pozzolan does not have substantial natural cementing properties. Examples of Class F pozzolans includes fly ashes made from anthracite coal and the Texas lignites.
Pozzolan, Natural
A pozzolan that occurs naturally. Such pozzolans include volcanic tuffs, volcanic ash, diatomaceous earth, some clay as well as other substances. Processing of natural pozzolans may include crashing, milling, drying, calcining, and air separation.
Pozzolan, Rio Grande, Class N
Rio Grande Pozzolan was one of the first natural pozzolans that was commercially produced in the United States. A natual pozzolan that was produced by Pozzolana, Inc. from volcanic ash in Starr County (Rio Grande City, IX), Tex. from the early 1950s through the 1960s. We periodically obtain samples of this volcanic ash and process it in the lab following the same procedure used by Pozzolana, Inc.
Pozzolanic Activity Index
An ASTM test where 20% of the Portland cement in a mix is replaced with the pozzolan to be tested. The pozzolanic activity index is the percentage of strength the replacement mix reaches at 7 days and 28 days when compared with a non-replacement mix. A minimum pozzolanic activity index of 70%/o is required after 7 days and 28 days. With this replacement level to a great extent the test reveals that the pozzolan passing this test does not have deleterious properties. Ground limestone with no pozzolanic properties has been known to pass the test. Discussions are underway to modify the test to require a higher level of substitution, possibly as high as 35%.
Stucco
A finish which traditionally is applied in three coats. A scratch coat, a brown coat, and a texture or finish coal
Stucco, Brown Coat
The second coat of stucco that is applied to a lath. It is used as a thickness builder and a leveling coat.
Stucco, Finish Coat
The third coat of stucco that is applied to a lath. It is used as a color coat and/or a texture coat.
Stucco, Scratch Coat
The first coat of stucco that is applied to a lath. It is usually scratched with horizontal striations to assist in a physical bond to the second coat.
Tri-Modal Particle Distribution
Normal particle distribution of a substance is a bell curve or a spike. With some fly ashes, the particle size distribution contains two or three spikes. With these spikes, the packing factor increases and the resulting packed fly ash has fewer voids than a product with a normal type distribution. Fewer voids usually equate to less water penetration through the mix.
Today mortar and stucco generally are defined as a mixture consisting of usually a cementitious binder, a fine aggregate, and water. A mortar typically is used to position and hold brick, block, stone, or other similar materials in to permanent position. A stucco typically is a finish which traditionally is applied in three coats and is used in plastering construction.
The cementitious binder in mortar can comprise hydraulic cements such as masonry cement (ASSM C-91) and mortar cement (ASTM C-1329), and the like, and in stucco can comprise hydraulic cements, such as stucco cement (ASTM-1328), and the like. Hydraulic cements simply are cements that set and harden by chemical interaction with water and are capable of doing so under water. These hydraulic cements typically are comprised of a variety of components including among other things Portland Cement and pozzolan(s), such as natural pozzolan, fly ash Class “F”, or combinations of “F” and fly ash Class “C”. Accordingly, numerous varieties of hydraulic cements exist today with one providing different advantages over the next.
Regardless of the numerous varieties of cements, this invention manages to improve upon the conventional technology of today by creating a balanced hydraulic cement composition comprising a pozzolan(s), Portland Cement, hydrated lime, and an air-entraining agent. The compositions of the invention meet the rigorous tests set forth for example in ASTM C-91 “N” and “S”, C-1329 “N”; 1328“S” and other ASTM testing procedures. At the same time, the mixes are relatively inexpensive due to the inclusion of extremely high ranges of fly ash and/or type “N” pozzolan therein.
In comparison testing of this invention using ASTM testing guidelines against other conventional masonry, mortar, and stucco cements, the mortars and stuccos produced by this invention required less mixing water, were less likely to effloresce, were less likely to develop fungal and algal growth, were more water resistant, exhibited autogenous healing continued to gain strength for over one yea when tested according to ASTM test procedures, were less likely to leak under high wind and rain conditions, and were less likely to burn the tradesmen's hands since the amount of alkali oxides and hydroxides are lower.